Method of treating a composite filament



Jan. 30, 1968 TQYQKAZU MATSUMOTQ- ET AL 3,365,873

METHOD OF TREATING A COMPOSITE FILAMENT Filed July 26, 1965 FIG. 2

FIG.

FIG.4

United States The present invention relates to a method of manufacturingknitted fabrics, and more specifically, to a method of manufacturingknitted fabrics having an excellcnt stretchability and an even surfaceappearance, which consists of imparting a twist or a false-twist to acomposite filament comprising two adherent different components ofsynthetic thermoplastic linear polymer with different shrinkabilitiesdisposed in a side-by-side or eccentric sheath-core relation withrespect to each other in the cross-section of the filament and knittingfabrics from said filament.

It is well known that stretchable knitted fabrics are obained by the useof crimped filaments. Likewise, knitted fabrics having a highstretchability may be obtained also by the steps: first manufacturingknitted fabric with fibers having potential crimpability and thereafterdeveloping crimps in the fibers in said knitted fabric. For filamentswith potential crimpability mentioned in the above, socalled compositefilaments may be used. The composite filament is obtained bysimultaneously, spinning through an orifice, two different polymershaving different shrinkabilities. This filament develops crimps by theapplication of a suitable after-treatment, for instance, a swelling orheating treatment. When knitted fabrics are manufactored with compositefilaments and by subsequent crimp development process, however, many ofsuch fabrics, especially those made with monofilameits, pre sentirregular or uneven stitches. This is a phenomenon which is caused bythe shrinking of the filaments or by the development of crimps infilaments. This phenomenon is known in terms of creping" or wrinkling.Such development of creping greatly affects the aesthetic appearance offinished knitted fabrics.

In view of he foregoing problems in the knitted fabrics made fromcomposite filaments, it is an object of the present inventon to obtainknitted fabrics made from composite filaments which have an even andwell-balanced superficial appearance as well as an excellentstretchability. More specifically, the present invention ischaracterized in that the composite filaments to be used are given atwist or a false-twist to such extent that the conjugate phase relativeto the length of filaments necessary for forming a unit stitch(hereinafter to be referred to as unit stitch length) may be turned byat least 20 degrees, in average, and preferably 30 degrees or morearound the axis of the filamen, before the filaments are knit intofabrics.

The objects and advantages of the present invention may be more clearlyunderstood by reference to the following detailed description includingselected embodiments when considered with the drawings in which:

FIG. 1 is a cross-sectional view of a composite filament;

FIG. 2 shows a composite filament in crimpcd state;

FIG. 3 is a side elevational view of a twisted composite filament; and

FIG. 4 is another side elevational view of a twisted composite filament.

The terms conjugate phase hereinabovc used means the direction in whichthe two components forming a filamentare disposed. In other words, inFIG. 1 of the drawings which shows a cross-section of a side-by-sideatent two-component filament having a circular cross-sectionalconfiguration, the straight line P-Q represents the boundmy line formedby the two components A and B. The direction of the said boundary lineperpendicular to the axis of the filament is called the conjugate phase.For example, when the locations of the two components A and B in thecross-section of a composite filament are exchanged with each other, thephase has turned by 180 degrees. In the same way, the conjugate phasesof various types of two-component filaments. in which the two componentsare eccentrically disposed may be defined. When the shrinkability of thecomponent B is greater than that of component A in FIG. 1, the filamentwill bend with the component B placed inside of the bends, by theapplication of heat-treatment, as shown in FIG. 2. If the conjugatephase of the said two-component filament was changed along the length ofthe filament, the filament would curl in a different direction withrespect to the three-dimensional space. In other words, the direction inwhich the filament will curl may be regarded as the conjugate phase.

Now, if the composite filaments forming several stitches aligned inadjacent relationship either in a Wale min a course of a knitted fabrichave the same conjugate phase, and especiallywhen the plane of thesurface of the knitted fabric lies in parallel with the boundary planeof two components in the side-by-side composite filaments, the filamentswill invariably curl in the same direction, developing, as a result, awavy contour on the surface of the knitted fabric. This phenomenon ismore often noted of mono-iiilament fabrics as a matter of fact, but notoften in multi-filament fabrics.

In order to accomplish the objects of the present in vention, thefilaments composing a knitted. fabric have to be processed so that theconjugate phase of the filaments may be forcibly distributed withsubstantial uniformity in all directions in th-reedimensional space bygiving the filaments a twist,.the angle of which is at least 20 degreesin average, and preferably 30 degrees or more per unit stitch length. Ifthere is a change of 30 degrees in the conjugate phase of one unitstitch, the total amount of the changes in the phase for threeadjacentstitches will be degrees, and as a result, there will develophardly any appreciable undulations of stitches in the knitted fabric. Itis usually not necessary, however, to change the phase to an extent ofmore'than 360 degrees per unit stitch length. In the present invention,the change of the conjugate phase of a filament is imparted by atwisting or false-twisting process. When a certain length of filament isturned or twisted by onecomplete revolution, the phase of the filamenthas been changed .by 360 degrees. In the case of false-twisting,however, the number of twists given to a filament as a whole is zero,but the filament still carries twisted portions and reversely twistedportions locally thereof, and thus the filament is given a sufficientamount of change in phase. In the case of falsetwisting, the amount oflocally existing twists is calculated as a value per unit stitch length.Namely, in the case of false-twisting, the total amount of the changesin conjugate phase in the length of the filament. including S-twists andZ-twists, is obtained by aggregating the absolute values of changedphases. The mean may be obtained by dividing the total amount by thelength of the filament.

FIG. 3 shows acomposite filament after being twisted. FIG. 4 shows thesame filament which has undergone false-twisting. Respective arrows showthe progress of changes in the conjugate phase. As is obvious from thedrawings, the twist in FIG. 3 and the false-twist in FIG. 4 may beconsidered to presentthe same effect. The amount of the changes inconjugate phase in both cases, which is obtained according to theforegoing method, is 360 degrees respectively. Twists and false-twistsneed not be uniformly distributed throughout the length of the hiament.The objects of the present invention may be attained by arranging theconjugate phase in such fashion that the phase may be reversed at every3 to 4 stitches, and preferably at every two stitches or one stitch.

The size of the stitches in knitted fabrics for wear are usuallyrestricted within a certain range. In many cases, the length offilaments constituting one unit stitch is in the range from 0.5 mm. toseveral millimeters. In seamless hosier for ladies, for example, theunit stitch length is in the range of 0.S3 mm., approximately.Therefore, the objects of the present invention may be accomplished bygiving the filaments to be used an amount of twist of at least 50 t./m.(turns/meter).

A false-twist may be given to a filament by the following steps. Namely,the filament is first twisted. This twisted filament is treated withheat either by dry heating or wet heating to fix the twist therein. Thenthe processed filament is further given a reverse twist so thatapparently the filament has been untwisted. By reason of the mutualactions between the primary fixed twist and the subsequent untwisting,the amount of local twist which was discussed above will be determined.Therefore, a highly effective local twist accruing from the twist byfirst twisting the filament to an extent of at least 100 t./m.,subsequently fixing the twist, and then apply ing substantially equalamount of reverse twist to the filament. 'I his false-twisting permitsremoval of residual torque in the filament, if any, by further heatingthe filament. The present invention is particularly effective for themanufacture of ladies seamless stockings having even and uniformsuperficial appearances. The present invention is most effective for themanufacture of knitted fabties with certain types of stitches which are:plain knitting of basic type and its modified types. The presentinvention is also effective for mesh knitting, run-proof knitting andother types of knitting, of which the surface conditions are highlyimproved.

Since the objects of the present invention are accomplished bydistributing the conjugate phase of filaments in multiple directions ina knitted fabric or fabrics in such manner as has been described, theeffect of this method is most remarkably displayed in fabrics knittedwith mono-filaments. The surface of fabrics knit with multitfilaments isobserved to be considerably even, because there is realized adistribution of conjugate phase in the multi-filaments themselves. Inmany cases, however, if the method of the present invention is used inknitting fabrics with multi-filaments, their uniformity in appearancewill be further enhanced.

Now, some examples of the present invention will be described. In theseexamples, polyamide composite filaments are used. It is to beunderstood, however, that the present invention is not restricted onlyto such filaments. It should be obvious that composite filamentscomprising any sort of polymers may be used in the method of the presentinvention so long as the filaments are of the type which can developcrimps.

EXAMPLE 1 Polycaproamide and a polymer obtained by polymerizing 15 partsof hexamethylenc diammonium tercphthalate and 85 parts of e-caprolactamin an atmosphere of nitrogen gas at 260 C. were simultaneously spuntogether through an orifice to form a side-by-side type filament withthe conjugation ratio of 1:1 by volume. The filament was then drawn atnormal temperature to a length 4.4 times its original length, and thus amonofilament of 15 deniers was obtained. A part of the filament thusobtained was given a twist of 20 turns per meter,

and another part of the filament was given a twist of 170 turns permeter. After fixing the twists in an oven at 70 C. for 10 minutes, thetwo parts of the filament were respectively placed on knitting machinesto knit the leg portions for womens seamless hosiery. The superficialappea ance of the stitches after knitting did not differ in any degreefrom that of ordinary nylon hosiery. These knitted specimens weretreated with saturated steam at 110 C. for minutes under relaxedconditions to develop crimps therein. After the fabrics were dyed, theywere placed on ordinary aluminirnum boards, and were set at 120 C. for45 seconds in saturated steam with subsequent drying. and cooling. Thus,seamless hosiery having high stretehability were obtained. The unitstitch length was 1--2 mm. In the case of the fabric knit with filamentshav ing a twist of 170 turns per meter, the changes of phase providedfor said filaments were noted to be 60-120 degrees per unit stitchlength, which showed that a satisfactory effect of the present inventionwas obtained.

EXAMPLE 2 A copolymer obtained by copolymerizing 4 parts of a salt ofnylon 66 and 6 parts of a salt of nylon 610 and having an intrinsicviscosity of 0.94 in metacresol at 30 C. and nylon 66 with an intrinsicviscosity of 0.31 under the same conditions were simultaneously spuntogether through an orifice at the conjugation ratio of 1:1 by volume toform a unitary filament, and after drawing the obtained filament to alength 4.4 times the original length at 105 C., a mono-filament of 15.3deniers was obtained. This filament was given a false-twist of 1,500turns per meter at heater temperature of 140 C. at the first feedingrate of minus 3% on the CS-3 type false-twister manufactored by ErnestScragg & Sons Limited, England, and then the filament was passed incontact with an aluminium plate heated at 120 C. for 0.3 second at thesecond feeding rate of minus 1% to erase the residual torque, and waswound up on a reel. The filament thus obtained was knit into astockingin the same manner as mentioned in Example 1. The stocking soobtained was found to have excellent stitch formation, marvelous elasticproperties and was wrinkle-free and superior to stockings made fromcomposite filaments which were not given false-twists.

EXAMPLE 3 A copolyamide having an intrinsic viscosity of 1.29 wasprepared by polymerizing a mixture of 90 parts of 6" caprolactam and 10parts of hexamcthylene diammonium terephthalate in an atmosphere ofnitrogen gas at 270 C. for 6 hours. This copolyamide and nylon 6 havingan intrinsic viscosity of 1.0 were simultaneously melt-spun togetherthrough a common orifice at the conjugation ratio of 1:1 by volume toform a side-by-side type composite filament. The spun filament was drawnto a length 3.9 times as long as the original length at roomtemperature, and a mono-filament of deniers was obtained. he samefilaments thus obtained were given twists of :./m., t./m., t./m., 30t./rn., t./m., t./m., t./m. and 220 t./m. respectively. These twistedfilaments were wound up on aluminium bobbins respectively. After heatingthe filaments at 70 C. for 15 minutes to fix the twists thereof, legportions of stockings were knit with these filaments respectively on a400-needle Scott and Williams, hosiery knitting machine manufactured bythe Scott and Williams, Inc., Laconia, N. H. The superfiicialappearanccs of the knitted fabrics were uniform and showed no differencefrom ordinary seamless stockings. The stocking fabrics thus knit weretreated in saturated steam at 107 C. without tension for 15 minutes todevelop crimps therein. After drying. the fabrics were placed onordinary aluminum boards to be set in saturated steam at 118 C. for 45seconds. After drying and cooling. the fabrics were removed from theboards, and thus stretchable stockings were obtained. Those fabrics madewith filaments given twisting of more than 60 t./m. showed improveddegree ssassra i i of evenness of the surfaces, and that of 100 t./m.showed perfectly wrinkle-free surface. Those of 120 t./m. or more didnot show an cllect much superior to the fabric of 100 t./m. Thesefindings are completely consistent with the theory of distribution ofconjugate phase described previously in this specification.

EXAMPLE 4 A bundle of mono-filaments of l5 deniers which were the sameas those used in Example 3 was given a Stwist of 1,500 t./m. and waswound up on an aluminium bobbin. The bobbin was placed in saturatedsteam at 70 C. for minutes to fix the twist of the filament. Afterdrying, the bundle of filaments was given reverse twist (Z- twist) of1,500 t./m. By fixing the reverse twiss in the same manner, local twistswere resulted in each filament. The bundle of the filaments wereseparated into five mon0- filaments. These mono-filaments were knit intoleg portions of seamless stockings in the same manner as was describedin Example 3. The obtained stretchable stockings exhibited remarkablyeven superliicial appearances.

What is claimed is:

1. A method comprising manufacturing stretchable knitted fabrics havingan even surface appearance from composite filaments constituted of twodifferent adherent components of synthetic thermoplastic linear polymers with different shrinkabilities, each filament having a tendency tocurl and form a wavy contour along its length, said-method including thesteps of twisting said filaments prior to knitting therewith to produceat least a 20 turn of the conjugate phase of the filament per length offilament corresponding to the unit stitch length of the fabric to beknit to prevent curling of the filament, knitting the thus twistedfilaments into fabric having the predetermined stitch length, andheating the thus knitted fabric to develop three dimensional crimps inthe filaments thereof.

2. A method as claimed in claim 1 wherein the twist of the phase isperiodically reversed.

3. A method as claimed in claim i. wherein the twist of the phase isperiodically reversed every 3 to 4- stitches.

4. A method as claimed in claim 1 wherein the twist of the phase isperiodically reversed every one to two stitches.

5. A method comprising manufacturing stretchable knitted fabrics havingan surface appearance from composite filaments constituted oi twodifferent adher-- ent components of synthetic thermoplastic linearpolymers with dillcrcnt shrinkabilities, each filament having a tendencyto curl and form a wavy contour along its length, said method includingthe steps of twisting said filaments prior to knitting therewith toproduce at least turns per meter of filament to prevent curling of thefilament, knitting the thus twisted filaments into a. fabric wherein thefilaments have a unit stitch length between 0.5 mm. and 3 mm, andheating the thus knitted fabric to develop three dimensional crimps inthe filaments thereof.

6. A method comprising manufacturing stretchable knitted fabrics havingan even surface appearance from composite filaments constituted of twodifferent adhercnt components of synthetic thermoplastic linear polymorewith. dill'ercnt hrinl-iahilitics, each filament having a tendency tocurl and form a wavy contour along its length, said method including thesteps of false tw sting said filaments prior to knitting therewith toproduce alternating twi-ts in the conjugate phase of each filament, eachsaid filament having a sum of the ab o'ute values of the twists which isat least 20 per length of the filament corresponding to the unit stitchlength of the fabric to be knit to prevent curling of the filament,.ltnitting the thus l'alsc twisted filaments into fabric having thepredetermined stitch length, and heating the thus knitted fabric todevelop three dimensional erimps in the filaments thereof.

'7. A method comprising manufacturing stretchable knitted fabrics havingan even surface appearance from composite filaments constituted or" twodillcrent adherent components of synthetic thermoplastic linear polymerswith different. shrinlrahilitics, each li'amcnt having a tendency tocurl and form a wavy contour along its length, said method including thesteps of imparting a twist to said filament of at least turns per meter,heatsetting the twist of said filament, applying to the said filamentsubstantially same amount of reverse twist as the first said twist toproduce local turns of the conjugate phase of the said filament of whichthe sum of the absolute value of the twists is al least 20" per lengthof the filament corresponding to the unit stitch length of the fabric tobe knit thereby to prevent curling of the filamerit, knitting the thustwisted filament into fabric having the predetermined stitch length andheating the thus knitted fabric to cevclop three-dimensional crimps inthe filaments thereof.

8. A method comprising treating a composite filament to enable thefilament to be knit into a fabric having an even surface appearance andsubstantial stretchability,

said filament icing composed of two adherent components of syntheticliarar thermoplastic polymers waving dillcrcnt shrinlntbilitics andjoined along a conjugate phase, the filament having a tendency to curland form a wavy contour along its length, said method including thesteps of twisting the filament to orient the couiugate phase indiffering directions along the length of the filament.

i A method as claimed in claim it wherein said conjugate phase iscontinuously twisted in one direction.

iii. A. method as claimed in claim 9 wherein said conjugatc phase istwisted in an amount about 50 turns per meter.

ll. A method as claimed in claim 8 wherein said conjugate phasealternately twist-ed in opposite directions. lit. A method as claimed inclaim ll wherein the sum of the absolute values of alternate twists isabout 50 turns per meter.

References Cited UNITED S'lriTES PA'liillT S 238.1504 4/1959 Biilon.2,931,091 4/1960 Breon 2l.l-72 3,009,312 11/1961 Scorn et al. 57-l 57'3,192,295 6/ 1965 Settcle m. 264-171 3,264,705 8/l966 Kovarik 28-7ZLGUlS K. RIMRODT, Primary Examiner.

8. A METHOD COMPRISING TREATING A COMPOSITE FILAMENT TO ENABLE THEFILAMENT TO BE KNIT INTO A FABRIC HAVING AN EVEN SURFACE APPEARANCE ANDSUBSTANTIAL STRETCHABILITY, SAID FILAMENT BEING COMPOSED OF TWO ADHERENTCOMPONENTS OF SYNTHETIC LINEAR THERMOPLASTIC POLYMERS HAVING DIFFERENTSHRINKABILITIES AND JOINED ALONG A CONJUGATE PHASE, THE FILAMENT HAVINGA TENDENCY TO CURL AND FORM A WAVY CONTOUR ALONG ITS LENGTH, SAID METHODINCLUDING THE STEPS OF TWISTING THE FILAMENT TO ORIENT THE CONJUGATEPHASE IN DIFFERING DIRECTIONS ALONG THE LENGTH OF THE FILAMENT.